Step - by- step



p 6, 1967 H. M. MARCHAL ETAL 3,344,275

X-RAY APPARATUS FOR STUDYING PERIODIC BQDILY PROCESSES CHARACTERIZED BYAN OSCILLATION OR PULSATION OF SOME BODY PORTION Filed Dec. 21, 1964 2Sheets-Sheet 1 p 26, 1957 H. M. MARCHAL ETAL 3,344,275

X-RAY APPARATUS FOR STUDYING PERIODIC BODILY PROCESSES CHARACTERIZED BYAN OSCILLATION OR PULSATION OF SOME BODY PORTION Filed Dec. 21, 1964 2Sheets-Sheet 2 mom I V 55 a J, m l r l l 1 O *1 '1 l 3\5 Q1 R2 I sou/m121 TC? TC;

, r6 I I 1i: *TAZ l i SOURCE FRO/1 L6. l :34 575p gy- 5TP 5 WITCH X-RAYAPPARATUS FGR STUDYING PERIODIC PRUCESSES (ZHARACTERIZED BY AN(ESCELLATION R PULSATIGN 0F SGME BQDY PORTHUN Henri Maurice Marchai,Paris, France, and Marie-Therese Marchal, born Dupuy, laris, France,assignors to Centre National de la Recherche Scientifique, Paris,France, a French Government Administration Filed Dec. 21, 1964, Ser. No.419,991 6 Claims. ((13. 250-415) ABSTRACT @E THE DISQLGSURE In aradiology apparatus for densigraphic examination there is effected asimultaneous recording on the one hand of relatively slow variations ofdensity of the obstacle that is examined due to its ventilation, and onthe other hand of small variations of density of the obstacle that isexamined due to the circulation of blood therein by making use in twodifferent channels of the intensity of the current delivered by a cell.Caculating means may be provided for directly combining together some ofthe informations thus simultaneously recorded for medical diagnosticpurposes.

This invention relates to radiology apparatus, and particularly toapparatus for applying radiological techniques to the study of thoseperiodic bodily processes which are characterized by an oscillation orpulsation of some body portion.

The present invention concerns novel radiographic devices for theperformance of densigraphic examinations in which a record is made ofthe relatively low frequency (i.e., less than 3 c.p.s.) variations inthe attenuation of a beam of X-rays, or other rays, modulated at itssource by a relatively high frequency (i.e., 50 to 190 c.p.s.) andtraversing a body under examination, said variations being a function ofthe variations in opacity which corresponds either to a variation indensity or in thickness of the body under examination. The presentinvention is particularly intended, because this application seems torepresent the most useful employ of the invention, for use in thediagnosis of the transparency of lungs by medical radiology.

This invention involves the provision, in combination with apparatus ofthe type discussed herein having means for converting, into variationsof electrical current, the variations of intensity of an X-ray beampassing through a subject, of first means for recording these variationsand/ or the average value thereof directly after amplification so as toobtain a measure of the relatively low-frequency variations in theopacity of the subject due to his breathing, and/or the average valuethereof, and second means for recording the signal obtained by theremoval of any carrier wave modulation applied to the X-ray beamfollowed by a substantially larger amplification than that produced bysaid first means, the resulting signal serving to indicate thevariations in opacity due to the subjects blood circulation.

Such apparatus could also comprise a computing arrangement for combiningthese signals in various ways in order to yield medically usefulrelations, such as, for example, a quantity representing the quotient ofthe amplitudes of the impulsions of the output from said secnitcd StatesPatent 0 M 3,344,275 Patented Sept, 26, 1967 0nd means divided by theoutput (either instantaneous or averaged) of said first means, the valueof which quotient is directly related to the blood flow rate in thesubject.

These and other objects, features, and advantages of the presentinvention will become more readily apparent from the following detaileddescription when considered together with the attached drawings, inwhich:

FIG. 1 is a schematic block diagram of a device employing one embodimentof the present invention;

FIG. 2 is a schematic diagram of a portion of the electronic circuit ofthe device of FIG. 1;

FIG. 3 is a schematic diagram of another portion of said electroniccircuit; and

FIG. 4 shows a pair of graphs which are useful in explaining theoperation of said other portion.

Before proceeding with a detailed description of preferred embodimentsof the invention, it would be well to review briefly the basic elementsof a densigraphic examination of, say, a portion of a lung.

The performance of such an examination involves essentially theformtaion of an image 1 (see FIG. 1) of the lung upon a radioscopescreen 2; a small fluorescent screen 26 (see (FIG. 2) is disposed in thepath of the rays having traversed the lung in the region to be examined,the image of this small screen on screen 2 is indicated at 3 in FIG. 1;and the light which the rays cause small screen 26 to emit is directedtowards a photo-cell 4 which transforms the received light energy intoan electric current whose variations are recorded.

In the prior art, the recording was made either: directly, after asimple amplification, so that an examination of the envelope of therecorded curve revealed the large amplitude, relatively low frequencyopacity variations caused by the ventilation or respiration of the lungportion being examined, and/or the average value of said opacity; orindirectly, after both a higher power amplification than in thepreceding case and a suppression of the high frequency modulation, orcarrier frequency, originally given to the rays, so that the final curverevealed the small opacity variations caused by the pulsating bloodcirculation occurring in the lung portion under examination.

If it were desired to investigate, both the respiratory operation andthe state of blood circulation in a given lung portion-which would be ofgreat value for certain diagnoses such as those of cancers of the lungs,emphysema, silicosis, etc.it was always necessary in the past to performtwo successive examinations each requiring a different apparatus. Thisprocedure caused the following major inconveniences:

One coud never be certain that the two examinations corresponded to asingle set of examining conditions because it is difiicult tosuccessively position two small fluorescent screens so that they willeach be opposite the same lung portion, the subject has a tendency tomove, and it is extremely diflicult to obtain the same respiration andblood circulation conditions for the two successive examinations;

The total duration of the two examinations was double that of a singleexamination; and

It was necessary to provide two fluorescent screens and two photocells.

The present invention proposes to eliminate these inconvenienccs bypermitting the two desired readings to be obtained simultaneously bysimultaneously applying the output current of a single detectingphotocell to two different signal processing circuits.

To this effect, a preferred embodiment of the invention is shown in FIG.1 to comprise an impedance converter 5 receiving the output signal fromcell 4 and applying this signal to two separate signal processingcircuits. One processing circuit comprises only an amplifier 6 and arecorder 7 producing a signal whose variation reveals the respirationpattern of the lung portion. The other circuit comprises, an addition toan amplifier 8, whose gain is greaetr than that of amplifier 6, and arecorder 9, a low-pass filter 10 which passes only those frequencycomponents of the photocell output which are below a certain frequency,10 c.p.s. for example.

Itthus results thattwo curves relating to exactly the same lung portionare recorded simultaneously, andpreferably on the same sheet 11. Thefirst curve 12 presents an envelope whose amplitude varies in accordancewith the overall opacity variations of the lung portion, these overallvariations corresponding generally with the respiration. The secondcurve 13 varies in accordance with the blood circulation. It should benoted that the oscillations (of l to 2 c.p.s.) represented in curve 13are also present in the envelope of curve 12, the principal frequency ofoscillation of this latter curve varying between 0 (when the subject isholding his breath) and 0.1 to 0.3 c.p.s. (when the subject is breathingnormally), but are not discernible therein as a practical matter sincethe amplitudes of these oscillations are around 100 times smaller thanthat of the respiration-induced oscillations of curve 12.

Comparison of these two curves should prove extremely valuable sincethey were both obtained under precisely the same conditions: such acomparison would enable one to determine, for example, whether atemporary and local stoppage of the blood circulation is related to arespiratory difficulty experienced by the subject.

Moreover, it takes no more time to obtain the two curves than itpreviously took to obtain a single curve and the number of photocellsrequired is reduced to one.

FIGURE 2 shows a circuit diagram of a portion of a circuit which may beused as part of the system of FIG. 1.

In this circuit, the output 14 from cell 4 is connected to groundthrough load resistor 15 and to the grid of a cathode follower triode 16whose principal function is to present a low output impedance whichserves to eliminate the effects of wiring capacities, particularly thatof the output lead from cell 4. The two electrical paths employed forthe production of curves 12 and 13, respectively, begin at two points 17and 1%, respectively, of a resistor 19 connecting the cathode of triode16 to a source of negative high voltage.

The first of these points 17, is connected to the grid of an amplifiertriode 20 whose cathode is connected to the negative high voltage sourcethrough a resistor 21 and whose anode is connected to another amplifierstage, indicated by 22, which is in turn connected to recorder 7.

The other point, 18, is connected to the grid of an amplifier triode 23whose cathode is connected to the negative high voltage through resistor24 and to filter 10. The output from filter 10 is connected tocomplementary amplifiers, indicated generally by 25, which are in turnconnected to recorder 9.

Filter 10 is advantageously constituted by at least two filters inseries separated by a cathode follower circuit which permits each filterto have a high output impedance.

It should of course be appreciated that any other known radiological orelectronic techniques may be used to improve the operation of theabove-described system without departing from the scope of thisinvention.

For example, in order to permit the small fluorescent screen, 26,forming the image 3 on the large screen 1 to be accurately positioned,it is desirable to render at least a part of the elements immediatelysurrounding screen 26 transparent to X-rays, the light produced by thescreen being transmitted to cell 4 by a light guide 27 which istransparent to X-rays, such an arrangement having been described inapplicants U.S. Patent No. 3,086,123, issued on April 16, 1963.

Because the present invention is capable of obtaining, at one time andduring the same examination, electrical signals indicating both theaverage opacity s of a lung portion and the amplitude, at, of theopacity modulation caused by blood pulsations, an improved embodiment ofthe present invention includes means for automatically computing theratio a/s which represents the circulatory coefiicien for the lungportion investigated.

One arrangement for attaining this result employs a value for a whichrepresents the average of the amplitudes of modulation created byseveral successive blood pulsations. This provision serves to correctfor the fact that opacity variations due to successive blood pulsationsare not exactly identical to one another.

One arrangement for carrying out such a computation is shown in FIGS. 1and 3 to comprise two peak-reading voltmeter assemblies 28 and 29receiving, respectively the outputs of amplifiers 6 and 8. Theseassemblies are activated by impulses emitted by an electrocardiographassembly 30, connected to the examined subject 33 and operating duringthe same time as the rest of the described apparatus, said emittedimpulses being formed through a Schmitt trigger 34.

The impulses produced by said trigger 34 enter in two step-by-stepswitches 35 comprised respectively by each assembly 28 and 29. So thefirst impulse activates in each of said assemblies only a first relay Rthrough a line L and a closed contact r of a relay R Said activationcloses the contact r of the relay R which causes a first capacitor C tocharge from the corresponding amplifier 6 (or 8), through a closedcontact 1- of the relay R, until attaining a charge corresponding to thepeak value of the current supplied to it at that instant by saidamplifier (this peak value corresponding to s for assembly 28 and to afor assembly 29). The next impulse from trigger 34 activates, in eachassembly 28 and 29, through the step-by-step switch 35 of said assembly,a line L and a closed contact r of the relay R only a second relay R Thecontact r of said second relay is then closed and a second capacitor Ccharges in its turn to the peak value .9 (or a of the correspondingcurrent delivered by the amplifier 6 (or 8) at said instant. The thirdimpulse isolates in its turn the two first capacitors C and C of eachassembly 28 and 29 and permits the amplifier outputs to charge a thirdpair of capacitors C and so on. After a predetermined number ofimpulsions, five for the described example, the following impulse comingfrom the trigger 4 activates, through the step-by-step switch 35 of eachassembly 28 and 29 and a line L the above mentioned relay R Saidactivation moves all the contacts r and consequently, activates all therelays R to R from a source 36 and connects all the capacitors C to C ofeach assembly 28 and 29 to inputs of a quotientmeter or ratiometer 31,which may be a logometer (sort of galvometer having two movable crossedframes and indicating the measured ratio by an angular deviation).

The output 32 furnished by meter 31, which indication may be in the formof a maximum angular deviation of the meter indicator, is proportionalto the relation between the sum a +a +a +a +a and the sum assuming thatfive capacitor pairs are used. In other words, the indication isproportional to the quotient of the average value a of the variation ofthe opacity of the portion examined due to the blood circulation dividedby the average value s of the absolute magnitude of this opacity.

it has previously been shown, by comparison with the results obtained bybronchospirometry and measurements of oxygen consumption, that thisquotient a/s is directly related to the actual blood circulation in theexamined region.

In practice, in order to reduce the number of blood impulsions utilizedfor obtaining the average values, and hence to reduce the number ofcapacitor pairs required in units 28 and 29, the examination may becarried out by having the subject take an average breath and hold it,with the result that all of the values s s etc., will be equal to theaverage s so that unit 23 may thus be simplified so as to comprise, forexample, a single chargeaccumulating capacitor.

The diagrams of FIG. 4 relate to just such a procedure; the upper curverepresents the continuous recording of amplitude s and the lower curveshows five successive oscillations, having peak amplitudes of a :1caused by the blood circulation.

It would of course be desirable to have the output 32 also recorded onsheet 11.

It thus results that there is produced a device which is so arranged andconstructed that a single photocell can be used to simultaneouslydetermine the curves of both the average opacity and the opacityvariation due to the blood circulation of the subject under study.

It should be noted that many variations can be made to theabove-described structure without departing from the spirit of thepresent invention, such variations including, among others:

Those wherein the apparatus is equipped with a plurality of smallscreens 26, each associated with a light cell and appropriate signalprocessing circuitry, in order to permit several lung portions to besimultaneously examined;

Those wherein the means for supplying an electric current proportionalto the intensity of the X-ray beam passing through the region underexamination are directly responsive to these rays (Geiger counter,ionization chamber, etc.) instead of being indirectly responsive theretothrough the intermediary of the fluorescent screen 26;

Those wherein the system of the present invention, rather than havingits input interposed between the X-ray source and the large screen 2,has it interposed between this latter screen and the observer in such away as to receive all or part of the light emitted by said screen;

Those wherein small screen 26 is constituted by a scintillator crystalcapable of transforming the radiant energy received (produced by X-raysor other radiation) into light;

Those wherein the large screen 2 is replaced by the reception window ofa brightness amplifier Coupled in a known manner to a televisionreceiver through the intermediary of a camera tube of the Vidicon type,or other type (which technique permits a reduction in the X-ray dosagereceived by the subject while improving the quality of the resultingimage); the resulting curves 12 and 13 might, with this arrangement, bereproduced on the screen of this receiver through the intermediary of asecond camera tube;

Those wherein the device might be associated with any other computerarrangement such as one capable of determining the quotient of, or thedifference between, average opacity values corresponding, respectively,to a forced inhalation and a forced exhalation by the subject, whichquotient or difiference could then be, automatically or not, added tosimilar quantities corresponding to other lung portions or to otherrelations of different types for various diagnostic purposes.

It should therefore be understood that the breadth of the presentinvention should be limited only by the scope of the attached claims.

What We claim is:

1. In a radiographic device for performing densigraphic examinations ona subject and comprising a source of a high-frequency modulated X-raybeam to be projected through the portion of the subject to be examinedand means detecting the beam after it has traversed the subject forproducing an electrical signal which varies in proportion to thevariation of the intensity of the X-rays passing through the portion ofthe subject under examination, the improvement comprising: firstelectronic signal processing circuitry having an input connected toreceive the signal produced by said detecting means and an output uponwhich appears an amplified version of said signal; second electronicsignal processing circuitry having an input connected to receive thesignal produced by said detecting means and an output upon which appearsa version of said signal from which said high-frequency modulation hasbeen removed and which is substantially more amplified than the outputof said first circuit; and recording means connected to simultaneouslyrecord the signals appearing on said two outputs.

2. A device as recited in claim 1 further comprising computing meansconnected to receive the outputs from both said signal processingcircuitries for producing a signal which is proportional to the quotientof the value of the peaks of the output of said second circuitry dividedby the output of said first circuitry.

3. A device as recited in claim 2 wherein said computing meanscomprises: first averaging means connected to the output of said firstcircuitry for obtaining a signal representing the value of the averageamplitude of the envelope of the output from said first circuitry;second averaging means connected to the output of said second circuitryfor obtaining a signal representing the average of several successivepeaks of the output signal of said second circuitry; and comparatormeans connected to said two averaging means for producing a signalrepresenting the quotient of the value of the signal obtained by saidsecond averaging means divided by the value of the signal obtained bysaid first averaging means.

4. A device as recited in claim 3, wherein said comparator means is aratiometer.

5. In a radiographic device for performing densigraphic examinations ona subject and comprising a source of a high-frequency modulated X-raybeam to be projected through the portion of the subject to be examinedand means detecting the beam after it has traversed the subject forproducing an electric signal which varies in proportion to the variationof the intensity of the X-rays passing through the portion of thesubject under examination, the improvement comprising: first electronicsignal processing circuitry having an input connected to receive thesignal produced by said detecting means and an output upon which appearsan amplified version of said signal; second electronic signal processingcircuitry having an input connected to receive the signal produced bysaid detecting means and an output upon which appears a version of saidsignal from which said high-frequency modulation has been removed andwhich is substantially more amplified than the output of said firstcircuitry; recording means connected to simultaneously record thesignals appearing on said two outputs and means connected to receive theoutputs from both said signal processing circuitries for producing asignal which is proportional to the quotient of the value of the peaksof the output of said second circuitry divided by the output of saidfirst circuitry, said computing means comprising first averaging meansconnected to the output of said first circuitry for obtaining a signalrepresenting the value of the average amplitude of the envelope of theoutput from said first circuitry; second averaging means connected tothe output of said second circuitry for obtaining a signal representingthe average of several successive peaks of the output signal of saidsecond circuitry; and comparator means connected to said two averagingmeans for producing a signal representing the quotient of the value ofthe signal obtained by said second averaging means divided by the valueof the signal obtained by said first averaging means, said first andsecond averaging of said impulses and adapted to connect all saidcharged capacitors on an input of said comparator means.

References Cited UNITED STATES PATENTS 2,679,598 5/1954 Wright et al.250 95 2,858,421 10/1958 Touvet 250 199 3,086,123 4/1963 Marchal 25071.5 3,109,058 10/1963 Luhn 346-35 RALPH G. NILSON, Primary Examiner.

A. L. BIRCH, Examiner.

1. IN A RADIOGRAPHIC DEVICE FOR PERFORMING DENSIGRAPHIC EXAMINATIONS ONA SUBJECT AND COMPRISING A SOURCE OF A HIGH-FREQUENCY MODULATED X-RAYBEAM TO BE PROJECTED THROUGH THE PORTION OF THE SUBJET TO BE EXAMINEDAND MEANS DETECTING THE BEAM AFTER IT HAS TRAVERSED THE SUBJECT FORPRODUCING AN ELECTRICAL SIGNAL WHICH VARIES IN PROPORTION TO THEVARIATION OF THE INTENSITY OF THE X-RAYS PASSING THROUGH THE PORTION OFTHE SUBJECT UNDER EXAMINATION, THE IMPROVEMENT COMPRISING: FIRSTELECTRONIC SIGNAL PROCESSING CIRCUITRY HAVING AN INPUT CONNECTED TORECEIVE THE SIGNAL PRODUCED BY SAID DETECTING MEANS AND AN OUTPUT UPONWHICH APPEARS AN AMPLIFIED VERSION OF SAID SIGNAL; SECOND ELECTRONICSIGNAL PROCESSING CIRCUITRY HAVING AN INPUT CONNECTED TO RECEIVE THESIGNAL PRODUCED BY SAID DETECTING MEANS AND AN OUTPUT UPON WHICH APPEARSA VERSION OF SAID SIGNAL FROM WHICH SAID HIGH-FREQUENCY MODULATION HASBEEN REMOVED AND WHICH IS SUBSTANTIALLY MORE AMPLIFIED THAN THE OUTPUTOF SAID FIRST CIRCUIT; AND RECORDING MEANS CONNECTED TO SIMULTANEOUSLYRECORD THE SIGNALS APPEARING ON SAID TWO OUTPUTS.